¹Jeremy Brossier,¹Francesca Altieri,¹Maria Cristina De Sanctis,¹Alessandro Frigeri,¹Marco Ferrari,¹Simone De Angelis,¹Enrico Bruschini,¹Monica Rasmussen,¹Janko Trisic Ponce
Journal of Geophysical Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009393]
¹Institute for Space Astrophysics and Planetology (IAPS), National Institute of Astrophysics (INAF), Rome, Italy
Published by arrangement with John Wiley & Sons

Extensive research over the past two decades has shown that early Mars likely had a warmer,wetter climate with widespread water activity. Ferromagnesian (Fe,Mg‐rich) clay deposits are compellingmarkers of these ancient environments, helping reconstruct Mars’ hydrologic evolution, assess past habitability,and guide future exploration. This study analyzes hyperspectral data from the Compact ReconnaissanceImaging Spectrometer for Mars (CRISM) aboard NASA’s Mars Reconnaissance Orbiter, focusing on regionsalong the Martian crustal dichotomy—where clay deposits occur at the boundary between the ancient southernhighlands and the younger northern lowlands. We systematically surveyed ∼1500 CRISM targeted observations(1–2.6 μm) to identify ferromagnesian clays, distinguish them from other hydrated minerals, and characterizecompositional differences between Fe‐ and Mg‐rich species using diagnostic absorptions around 1.4, 2.3, and2.4 μm. Results reveal spatial variations in clay mineralogy: Fe‐rich nontronites are prevalent around MawrthVallis, while Mg‐rich saponites are more locally distributed in Nili Fossae and Libya Montes. Oxia Planum—the Rosalind Franklin rover landing site—exhibits more compositionally intermediate clays such asvermiculites and ferrosaponites. These differences may reflect variations in the iron and magnesium abundanceor in the iron oxidation state. Moreover, a recurring absorption near 2.5 μm suggests co‐occurring carbonateslike magnesite and siderite, increasing the potential for biosignature preservation. These findings refine ourunderstanding of Mars’ aqueous history and offer an important mineralogical context for future rover andsample return missions. They also emphasize the need for a next‐generation orbital imaging spectrometer tosucceed CRISM and extend its legacy.

¹E. Dobrică,¹A. N. Krot,²A. J. Brearley
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70102]
¹Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Mānoa, Hawai‘i, USA
²Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico, USA
Published by arrangement with John Wiley & Sons

Returned regolith samples from the asteroid Itokawa provide a unique opportunity to compare shock metamorphic effects in unconsolidated regolith materials with those preserved in lithified meteorites, that is, megaregolith. We analyzed four Itokawa particles (Ueda—RA-QD02-0519, Narahara—RA-QD02-0573, Domon—RA-QD02-0588, Ishiuchi—RX-MD03-0212) containing phosphates (merrillite and apatite) to assess their impact history. To place these observations in context, we also describe the associated mineral assemblages (silicates and chromite). While both space weathering effects, irradiation and impact, are present, the primary focus of this study is on impact-related modifications. We identified microcratering with a density comparable to that measured for Murchison, rare comminution effects in subsurface regolith materials, localized melting and vaporization, and partial decomposition of chromite into a high-pressure Fe2Cr2O5 phase (modified ludwigite-type). The two apatite crystals analyzed lack any brittle deformation; however, one shows strong submicron-scale chlorine heterogeneity and porosity that are consistent with partial melting and volatile redistribution. In contrast, the two merrillite grains, identified in two different particles, contain dislocations. Their microstructures indicate distinct shock histories: one particle preserves only limited, localized deformation probably induced by micrometeoroid impacts, whereas the other shows extensive brittle deformation features consistent with a more pervasive shock event. The combination of ductile and brittle deformation, along with melting and comminution, reflects a more intense and spatially extensive shock metamorphic process. Dislocation densities are comparable to those observed in ordinary chondrites (OCs) of shock stage S2 (5–10 GPa). This study shows that phosphates in Itokawa regolith record highly localized and heterogeneous shock metamorphic overprints, in contrast to the more uniform relationship between shock metamorphic stage and phosphate deformation described in megaregolith OCs. Phosphates are sensitive shock metamorphic tracers in asteroidal regolith, but meteorite-based calibrations must be applied cautiously to unconsolidated materials.